Water Testing and GAPs

Published: May 1, 2014

What one's water is tested for at most farms will fall into one of two categories:

• Being potable (so you can wash produce with it); you can then also use it for pesticide sprays which contact produce that may be eaten raw (e.g. tomatoes, green beans or leafy greens), or any irrigation uses.
• Not being potable. At the current time for the USDA GAPs audit, there are no specific guidelines for preharvest water usage. It is up to the producer to decide how high the levels of total coliform and E. coli CFU (colony forming units) to use, and what to do (if anything) if the producer feels the levels are too high. Pesticides mixed from non-potable water should not be applied directly to produce which may be consumed raw, but could be applied to crops like sweet corn, potato foliage, or pumpkins.

By far the least expensive and simplest way to test water is with the county health department, which has a courier service to get your water to a state lab. The cost is only $10 per sample, but they will not accept surface water sources and only test to see if it is potable.

Most growers should have at least some potable water, for drinking water and for certain pesticide applications. GAPs certification will require that this water is sampled and submitted annually. Any other well water, even if only for field irrigation, could be submitted at that same time. If it passes, then that is all you need to do. It could smell like rotten eggs and be an awful color, such that you’d never drink it, but it only matters that it passes the microbial testing. What do you do if your well does not pass the potable test, or is a surface source (e.g. pond or stream)?

Unfortunately, you then need to get it tested at a lab that can provide a number count for total coliform and E. coli CFU. We have chosen to provide two labs (later in this article) which provide this service. Both ask that growers contact them to get sample bottles and instructions for submission. Since the samples need to be received the following day, one will have to express mail the sample, unless delivery is reliable within a single day by UPS for ground service.

So why even test water that you can use anyway? Because guidelines are being developed on allowable levels for irrigation water, and the USDA GAPs inspector would be able to alert a grower if their source was a possible problem. Then the grower could consider what action might be taken to reduce the microbial levels. [The Food Safety Modernization Act may eventually provide water testing guidelines, but the proposed rule has been withdrawn for revision, and water testing was one area that will likely be revised. Thus what the GAPs inspectors are currently using is the most important for now.]

To submit water sample to a county health department, contact them directly (http://health.mo.gov/living/lpha/lphas.php). You will need to get a sampling kit from them. [Should you need their contact information, feel free to contact a nearby MU Specialist, either by phone or in writing. Our office support staff should be able to find the county health department information if we are not in the office.] This is a time-sensitive test so you need to find out when the courier leaves for the lab, and from where. Say that’s at 11 a.m. in your county. Collect the sample according to the kit’s directions, transport it back to your county health department before 10 a.m., in a cooler to keep the sample cool and away from light, so it gets on the delivery truck to the lab in Jefferson City the same day. Sample Monday through Thursday (excluding holidays), to assure the sample is tested within 24 hours.

• To submit ‘non potable’ or ‘surface’ water for testing, contact a lab providing this service directly. Listed below are two which do and have good customer service. There are certainly other labs that also provide this service, but we were unable to find a comprehensive list for labs that do so, and which provide customer service expected by the general public.
• Midwest Labs (https://www.midwestlabs.com) — The cost is $20 and is called 'Generic E. coli and Total Coliforms'. But they request you contact them ahead of time. They will ship you the correct sample containers and form to fill out. Phone: 402-334-7770. The test is under the 'Environmental-microbiology' area. Unfortunately, only NW Missouri is close enough to Midwest Labs for Ground Rate UPS to deliver to them the next day. Thus, next day shipping would have to be used for other areas of Missouri, at a significant increase in shipping cost.
• Penn State University (http://agsci.psu.edu/aasl/water-testing/drinking -water-testing) - They provide a 'Total Coliform and E. coli' test for $35, under Drinking Water Individual Test (Bacteria), for surface sources (but non potable well water is accepted, too). Contact their lab for a 'Drinking Water Test Kit'. Phone: 814-863-0841.

Sampling your well or surface source: For a well, sample as close to the well head as practical. Many county health departments provide the option where they will sample for you, at a very reasonable charge. This may be worth considering if getting to the pick-up/drop off point may be difficult. Wells need to be sampled annually.
For surface water like a pond, use the nearest point of contact which is usually where the pump lines hook up to the drip lines or out of the sprinkler nozzles. [The best water from a pond is at 18 to 36 inches below the surface. Consider this for your pump intake.] Surface water sources are often sampled quarterly, thus if one samples a pond in May, and will continue to irrigate into September, another sample should be taken again in August. However, the GAP inspector may suggest more frequent testing based on one’s results.

Samples should be kept cool; if shipping a sample, the lab should provide instructions for keeping the sample cool during transit.